Trap-jaw ants (Odontomachus sp.) use ballistic jaw propulsion for predator avoidance during interactions with antlions

Insects have a wide variety of jumping mechanisms that can be used to increase the probability of surviving predatory attacks. Trap-jaw ants are known for their rapid and powerful mandible strikes, but in certain contexts, Odontomachus species have been observed to direct those strikes not at prey but at the substrate, thereby launching themselves into the air. These could be escape jumps but have never been studied in a context that the ants might actually encounter in the field. We studied the use of ballistic jaw propulsion in Odontomachus brunneus during their interactions with a common ant predator: pit-building antlions (Myrmeleon). We observed that while trap-jaw ant workers escaped from antlion pits by running in 48% of interactions, in 18% of interactions they escaped by jumping. To test whether jumping improved individual survival, we experimentally restrained worker mandibles and measured the ants' escape rate. Workers with unrestrained mandibles escaped from antlion pits significantly more frequently than workers with restrained mandibles (G² = 13.2, P = 0.002). To determine whether there is variation in the use of the escape jump, we also compared the escape success of O. brunneus with the sympatric species Odontomachus relictus. While there was no significant difference in escape success (G² = 0.66, P = 0.4), O. relictus was never observed jumping out of antlion pits, suggesting that they might not use the escape jump in this context. Our results indicate, then, that some trap-jaw ants can use mandible-powered jumps to escape from common ant predators.